From ec03a03cf5d502a68d56fbcdbeed310142089736 Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Thu, 5 Mar 2026 08:22:48 -0600
Subject: [PATCH] fix: completely silence logs for noisy health check endpoints

Created FilterNoisyLogs plug that disables Phoenix logging for both
request and response logs by setting conn.private.phoenix_log to false.

This prevents both:
- Initial request log (Plug.Telemetry)
- Response log (Phoenix.Logger "Sent 200 in Xms")

Filters:
- GET /health (Kubernetes probes)
- HEAD / (external uptime monitors)
---
 lib/towerops_web/endpoint.ex                | 11 ++------
 lib/towerops_web/plugs/filter_noisy_logs.ex | 28 +++++++++++++++++++++
 2 files changed, 30 insertions(+), 9 deletions(-)
 create mode 100644 lib/towerops_web/plugs/filter_noisy_logs.ex

diff --git a/lib/towerops_web/endpoint.ex b/lib/towerops_web/endpoint.ex
index cbefd4e4..f9abc19c 100644
--- a/lib/towerops_web/endpoint.ex
+++ b/lib/towerops_web/endpoint.ex
@@ -51,12 +51,11 @@ defmodule ToweropsWeb.Endpoint do
 
   plug Plug.RequestId
   plug ToweropsWeb.Plugs.RemoteIpLogger
+  plug ToweropsWeb.Plugs.FilterNoisyLogs
   plug ToweropsWeb.Plugs.BruteForceProtection
   plug ToweropsWeb.Plugs.SecurityHeaders
 
-  plug Plug.Telemetry,
-    event_prefix: [:phoenix, :endpoint],
-    log: {__MODULE__, :log_level, []}
+  plug Plug.Telemetry, event_prefix: [:phoenix, :endpoint]
 
   plug Plug.Parsers,
     parsers: [:urlencoded, :multipart, :json],
@@ -91,10 +90,4 @@ defmodule ToweropsWeb.Endpoint do
   plug Plug.Head
   plug Plug.Session, @session_options
   plug ToweropsWeb.Router
-
-  # Disable logging for health check endpoint to reduce log noise from K8s probes
-  def log_level(%{path_info: ["health"]}), do: false
-  # Disable logging for HEAD requests to root path (external uptime monitors)
-  def log_level(%{method: "HEAD", path_info: []}), do: false
-  def log_level(_), do: :info
 end
diff --git a/lib/towerops_web/plugs/filter_noisy_logs.ex b/lib/towerops_web/plugs/filter_noisy_logs.ex
new file mode 100644
index 00000000..41b71ee4
--- /dev/null
+++ b/lib/towerops_web/plugs/filter_noisy_logs.ex
@@ -0,0 +1,28 @@
+defmodule ToweropsWeb.Plugs.FilterNoisyLogs do
+  @moduledoc """
+  Disables Phoenix logging for noisy endpoints that don't need to be logged.
+
+  This prevents both the initial request log (via Plug.Telemetry) and the
+  response log (via Phoenix.Logger) by setting conn.private.phoenix_log to false.
+
+  Currently filters:
+  - GET /health (Kubernetes health checks)
+  - HEAD / (external uptime monitors)
+  """
+  import Plug.Conn
+
+  def init(opts), do: opts
+
+  def call(conn, _opts) do
+    if should_filter?(conn) do
+      # Setting phoenix_log to false prevents Phoenix.Logger from logging this request
+      put_private(conn, :phoenix_log, false)
+    else
+      conn
+    end
+  end
+
+  defp should_filter?(%{method: "GET", path_info: ["health"]}), do: true
+  defp should_filter?(%{method: "HEAD", path_info: []}), do: true
+  defp should_filter?(_), do: false
+end